Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Additive vs. high grade gasoline

I read your article regularly and I really enjoy your sense of humor. I have
read that better grade gasoline, like Shell, or Mobil is useful to help clean
the engine. I’m a cheap Italian and I don’t want to pay an extra .20 or .30
cents a gallon. If I buy the additive from the store and add it to the fuel,
will I get the same result? If I use it every few months or by a certain
mileage mark, will I get the same result as using the higher grade gasoline?
From Reno, the cheap Italian :it:

First of I don’t know who your are addressing your post to. Just use tier one fuel of the grade your vehicle calls for and drive on. If it makes you feel good you can put an additive in the tank but I think you will be wasting money.

I don’t know where you live . . .

If you live in the US, I advise you to keep it simple

Use top-tier rated fuel. It has all the additives you could want, and you won’t get your hands messy dumping additional additives in the tank

If you’re a Costco member, start filling up there. Their fuel is top-tier rated

I can personally attest that top-tier fuel permanently took care of a fuel sending unit problem on one of our vehicles. Instantly, I might add

So if your car requires 87 octane . . . as many/most do . . . use top-tier rated fuel, at every fill-up you’ll get all those additives, and you won’t have to spend that additional money for mid- or premium-grade fuel

Win-win :smiley_cat:



If the OP lives in The US, here is a link to a list of the petroleum companies whose stations sell Top-Tier certified gas:

In the event that the OP doesn’t have any Top Tier stations in his neck of the woods, then I would suggest using a bottle of Techron fuel system cleaner once or twice a year.

1 Like

If by “high grade” gasoline you mean top tier gas, that’s one thing, but if you’re referring to high octane gas, don’t waste your money buying it unless you’re driving a high compression vehicle that requires or recommends it.

BTW, Tom has passed on and Ray doesn’t participate in this forum, at least as far as we know. I suppose there is a remote chance he is lurking here under an alias.

1 Like

There was/is a regular who made STRONG suggestions that Ray was indeed participating under an alias. I believe this regular said he recognized Ray’s personality, or something along those lines

Whether it’s true or not, it doesn’t have any bearing on this discussion, as far as I know

The station I was owner/operator of in the 1970s is now selling 110 octane zero ethanol racing gas for $3.20 per gallon. Not a bad price for vintage high compression muscle cars.

1 Like

I addressed that issue because the OP seemed to address the author of the referenced article.

The octane rating of ethanol is 108.

That’s less than our 90 octane non-alcoholic gas.

But it has a blending value of 113, that is, small amounts of ethanol blended with gasoline raises the octane rating of the mixture as if ethanol has a 113 octane rating.
It’s a case where the total is more than the sum of the parts.

1 Like

Use whatever your owner’s manual recommends. If it recommends no less that high octane, use high octane. If it recommends Top-Tier, use Top Tier. If it recommends 87 octane, use 87 octane.

Modern fuels (in the U.S.A.) all contain sufficient detergents to keep your engine clean internally as long as it’s driven regularly. Additives are unnecessary and added expense unless you’re trying to deal with an operating problem.
NOVA had a one hour special on gasoline and additives. Turns out that the chemistry of the modern additives packages is so highly refined across the industry that there’s no real difference between the different brands, and the companies within the same region (part of the country) all draw their fuel from the same supply distribution pipes. In short, if you’re buying 87 octane from Exxon in Florida you’re getting the same thing as if you were buying 87 octane from Irving in Florida. The differences are all marketing. I trust what NOVA says more than I trust what gas companies say by a very long longshot.

The biggest variable is how busy the gas station is. In rural areas of the Midwest there are probably countless stations that have more business in their greasy-spoon restaurant than at their pumps. I’d be leery of those.

Of course, if you’re posting from Italy… I have no clue. :stuck_out_tongue_winking_eye:

Are you saying that Top Tier quality fuel is a hoax? There is no difference in detergents between fuel companies?


If the seller doesn’t use ethanol to raise the octane level, what chemical do they use?

Edited to add 3 letters to improve clarity.

Lead??? (Body seems unclear, is it a complete sentence?) JEEESH!!!

I think lead would be illegal, and MTBE would likely be illegal, too. There may still be places where MTBE is legal. There are other octane enhancing chemicals. I’m just curious.

1 Like

Yes. But I don’t expect you to agree.
Watch the NOVA special if you can find it. It might open your eyes. Emphasis on “might”.

1 Like

Gasoline is basically a mixture of heptane and octane (iso-octane). The octane rating is increased by simply increasing the octane to heptane ratio.

Good to know. I meant to observe that ethanol raises octane while most correspondents to this forum disparage it vigorously.

That’s the original model, and still applicable - but you can’t get over 100 with pure octane. Some clever fellow figured out you could get a fuel that detonated at higher compression by adding tetraethyl lead instead of using a higher percentage of octane, that that was cheaper, and every gasoline I’ve ever known about has its octane number boosted by some additive, not more octane; that’s why there’s a bunch of different kinds of octane rating/number/…

Not true. There are many components to gasoline, from C4 to C12, mixed in ways to meet lots of different specs. Check out the Wikipedia article on gasoline for more info:
“The bulk of a typical gasoline consists of hydrocarbons with between 4 and 12 carbon atoms per molecule (commonly referred to as C4-C12).[4] It is a mixture of paraffins (alkanes), cycloalkanes (naphthenes), and olefins (alkenes), where the usage of the terms paraffin and olefin is particular to the oil industry.”